Reentrant violation of special relativity in the low-energy corner

In the effective relativistic quantum field theories the energy region, where the special relativity holds, can be sandwiched from both the high and low energies sides by domains where the special relativity is violated. An example is provided by 3He-A where the relativistic quantum field theory emerges as the effective theory. The reentrant violation of the special relativity in the ultralow energy corner is accompanied by the redistribution of the momentum-space topological charges between the fermionic flavors. At this ultralow energy an exotic massless fermion with the topological charge $N_3=2$ arises, whose energy spectrum mixes the classical and relativistic behavior. This effect can lead to neutrino oscillations if neutrino flavors are still massless at this energy scale.Comment: RevTeX file, 5 pages, one figure, submitted to JETP Let

Quark and Lepton Mass Patterns and the Absolute Neutrino Mass Scale

We investigate what could be learned about the absolute scale of neutrino masses from comparisons among the patterns within quark and lepton mass hierarchies. First, we observe that the existing information on neutrino masses fits quite well to the unexplained, but apparently present regularities in the quark and charged lepton sectors. Second, we discuss several possible mass patterns, pointing out that this quite generally leads towards hierarchical neutrino mass patterns especially disfavoring the vacuum solution.Comment: final version to be published in PRD, 5 pages, 2 figures, RevTe

Neutrino masses, cosmological bound and four zero Yukawa textures

Four zero neutrino Yukawa textures in a specified weak basis, combined with $\mu\tau$ symmetry and type-I seesaw, yield a highly constrained and predictive scheme. Two alternately viable $3\times3$ light neutrino Majorana mass matrices $m_{\nu A}/m_{\nu B}$ result with inverted/normal mass ordering. Neutrino masses, Majorana in character and predicted within definite ranges with laboratory and cosmological inputs, will have their sum probed cosmologically. The rate for $0\nu\beta\beta$ decay, though generally below the reach of planned experiments, could approach it in some parameter region. Departure from $\mu\tau$ symmetry due to RG evolution from a high scale and consequent CP violation, with a Jarlskog invariant whose magnitude could almost reach $6\times 10^{-3}$, are explored.Comment: Published versio

Where to look for solving the gauge hierarchy problem?

A mass of the Higgs boson close to 126 GeV may give a hint that the standard model of particle physics is valid up to the Planck scale. We discuss perspectives for the solution of the gauge hierarchy problem at high scales. Scenarios with an ultraviolet fixed point have predicted a Higgs boson mass very close to 126 GeV if the fixed point value of the quartic scalar coupling is small. In this case the top quark pole mass should be close to 172 GeV.Comment: additional references, somewhat extended discussion, 5 page

On the structure of the scalar mesons f0(975)f_0(975) and a0(980)a_0(980)

We investigate the structure of the scalar mesons $f_0(975)$ and $a_0(980)$ within realistic meson-exchange models of the $\pi\pi$ and $\pi\eta$ interactions. Starting from a modified version of the J\"ulich model for $\pi\pi$ scattering we perform an analysis of the pole structure of the resulting scattering amplitude and find, in contrast to existing models, a somewhat large mass for the $f_0(975)$ ($m_{f_0}=1015$ MeV, $\Gamma_{f_0}=30$ MeV). It is shown that our model provides a description of $J/\psi\rightarrow\phi\pi\pi/\phi KK$ data comparable in quality with those of alternative models. Furthermore, the formalism developed for the $\pi\pi$ system is consistently extended to the $\pi\eta$ interaction leading to a description of the $a_0(980)$ as a dynamically generated threshold effect (which is therefore neither a conventional $q\overline{q}$ state nor a $K\overline{K}$ bound state). Exploring the corresponding pole position the $a_0(980)$ is found to be rather broad ($m_{a_0}=991$ MeV, $\Gamma_{a_0}=202$ MeV). The experimentally observed smaller width results from the influence of the nearby $K\overline{K}$ threshold on this pole.Comment: 25 pages, 15 Postscript figure

Atmospheric and Solar Neutrino Masses from Horizontal U(1) Symmetry

We study the neutrino mass matrix in supersymmetric models in which the quark and charged lepton mass hierarchies and also the suppression of baryon or lepton number violating couplings are all explained by horizontal $U(1)_X$ symmetry. It is found that the neutrino masses and mixing angles suggested by recent atmospheric and solar neutrino experiments arise naturally in this framework which fits in best with gauge-mediated supersymmetry breaking with large $\tan\beta$. This framework highly favors the small angle MSW oscillation of solar neutrinos, and determine the order of magnitudes of all the neutrino mixing angles and mass hierarchies.Comment: No figures. 14 pages, revte

A_4 Symmetry and Lepton Masses and Mixing

Stimulated by Ma's idea which explains the tribimaximal neutrino mixing by assuming an A_4 flavor symmetry, a lepton mass matrix model is investigated. A Frogatt-Nielsen type model is assumed, and the flavor structures of the masses and mixing are caused by the VEVs of SU(2)_L-singlet scalars \phi_i^u and \phi_i^d (i=1,2,3), which are assigned to {\bf 3} and ({\bf 1}, {\bf 1}',{\bf 1}'') of A_4, respectively.Comment: 13 pages including 1 table, errors in Sec.7 correcte

Four Light Neutrinos in Singular Seesaw Mechanism with Abelian Flavor Symmetry

The four light neutrino scenario, which explains the atmosphere, solar and LSND neutrino experiments, is studied in the framework of the seesaw mechanism. By taking both the Dirac and Majorana mass matrix of neutrinos to be singular, the four neutrino mass spectrum consisting of two almost degenerate pairs separated by a mass gap $\sim 1$ eV is naturally generated. Moreover the right-handed neutrino Majorana mass can be at $\sim 10^{14}$ GeV scale unlike in the usual singular seesaw mechanism. Abelian flavor symmetry is used to produce the required neutrino mass pattern. A specific example of the flavor charge assignment is provided to show that maximal mixings between the $\nu_\mu-\nu_\tau$ and $\nu_e-\nu_s$ are respectively attributed to the atmosphere and solar neutrino anomalies while small mixing between two pairs to the LSND results. The implication in the other fermion masses is also discussed.Comment: Firnal version to appear in PR

Tribimaximal Neutrino Mixing and a Relation Between Neutrino- and Charged Lepton-Mass Spectra

Brannen has recently pointed out that the observed charged lepton masses satisfy the relation m_e +m_\mu +m_\tau = {2/3} (\sqrt{m_e}+\sqrt{m_\mu}+\sqrt{m_\tau})^2, while the observed neutrino masses satisfy the relation m_{\nu 1} +m_{\nu 2} +m_{\nu 3} = {2/3} (-\sqrt{m_{\nu 1}}+\sqrt{m_{\nu 2}}+\sqrt{m_{\nu 3}})^2. It is discussed what neutrino Yukawa interaction form is favorable if we take the fact pointed out by Brannen seriously.Comment: 13 pages, presentation modifie

Meson loop effects in the NJL model at zero and non-zero temperature

We compare two different possibilities to include meson-loop corrections in the Nambu-Jona-Lasinio model: a strict 1/N_c-expansion in next-to-leading order and a non-perturbative scheme corresponding to a one-meson-loop approximation to the effective action. Both schemes are consistent with chiral symmetry, in particular with the Goldstone theorem and the Gell-Mann-Oakes-Renner relation. The numerical part at zero temperature focuses on the pion and the rho-meson sector. For the latter the meson-loop-corrections are crucial in order to include the dominant rho -> pipi-decay channel, while the standard Hartree + RPA approximation only contains unphysical qqbar-decay channels. We find that m_\pi, f_\pi, and quantities related to the rho-meson self-energy can be described reasonably with one parameter set in the 1/N_c-expansion scheme, whereas we did not succeed to obtain such a fit in the non-perturbative scheme. We also investigate the temperature dependence of the quark condensate. Here we find consistency with chiral perturbation theory to lowest order. Similarities and differences of both schemes are discussed.Comment: 51 pages, 18 figures, to be published in Physics of Atomic Nuclei, the volume dedicated to the 90th birthday of A.B. Migdal, error in Eq. 4.22 correcte